(891.5) The Stress Hormone ACTH Causes a Prolonged Reduction in Heart Rate Variability

Poster Board Number: E379

J.W. Hamner (Spaulding Hospital Cambridge), J. Andrew Taylor (Spaulding Hospital Cambridge, Spaulding Hospital Cambridge), Istvan Bonyhay (Beth Israel Deaconess Medical Center, Beth Israel Deaconess Medical Center), Gail Adler (Brigham and Womens Hospital, Brigham and Womens Hospital, Brigham and Womens Hospital), Roy Freeman (Beth Israel Deaconess Medical Center, Beth Israel Deaconess Medical Center)

Hypoglycemia is a complex stressor that activates multiple hormonal systems and the sympathetic nervous system. Hypoglycemia also impairs autonomic control of blood pressure. It is possible that stress hormones produced during hypoglycemia (such as ACTH) play a role in the attenuation of autonomic function after recurrent hypoglycemia known as “cardiovascular hypoglycemia-associated autonomic failure”. Prior work from this placebo-controlled cross-over study has shown that ACTH infusion reduces Modified Oxford baroreflex gain and that the reduction persists to the following day. The purpose of this analysis was to determine whether measures of heart rate variability (HRV) demonstrate a similar pattern. In the original study, men and women aged 18 – 55 years (n = 22) completed 2 study visits (ACTH or placebo in random order) with a 1–3-month washout period between. A study visit consisted of a 3-day/2-night inpatient stay with the infusion occurring on day 2. Standard HRV measures from 3 minutes of 0.1 Hz breathing (6 breaths/minute) were collected on each of the 3 days. Overall HRV (time or frequency domain), as well as low frequency HRV, were reduced on the infusion day and the day after by ACTH, with no effect on blood pressure variability. Low-frequency transfer function gain was similarly reduced, but only on day 3. In addition, these frequency domain gains were significantly correlated with the Modified Oxford derived gains. These results suggests that the ACTH impairment of autonomic control of blood pressure is reflected in HRV measures.

This work was supported by the National Institutes of Health (NIH) (NIH R01 HL 01025319 to R.F.) (NIH K24 HL 103845 to G.K.A.); Harvard Catalyst, The Harvard Clinical and Translational Science Center (supported by National Center for Advancing Translational Sciences, NIH Award UL1 TR001102 and financial contributions from Harvard University and its affiliated academic health-care centers).